Plant infections caused by fungi lead to significant crop losses worldwide every year.
This study aims to better understand the plant defence mechanisms regulated by red
light, in particular, the effects of red light at night when most phytopathogens are
highly infectious. Our results showed that superoxide production significantly increased
immediately after red light exposure and, together with hydrogen peroxide levels,
was highest at dawn after 30 min of nocturnal red‐light treatment. In parallel, red‐light‐induced
expression and increased the activities of several antioxidant enzymes. The nocturnal
red light did not affect salicylic acid but increased jasmonic acid levels immediately
after illumination, whereas abscisic acid levels increased 3 h after nocturnal red‐light
exposure at dawn. Based on the RNAseq data, red light immediately increased the transcription
of several chloroplastic chlorophyll a‐b binding protein and circadian rhythm‐related
genes, such as Constans 1 , CONSTANS interacting protein 1 and zinc finger protein
CONSTANS‐LIKE 10. In addition, the levels of several transcription factors were also
increased after red light exposure, such as the DOF zinc finger protein and a MYB
transcription factor involved in the regulation of circadian rhythms and defence responses
in tomato. In addition to identifying these key transcription factors in tomato, the
application of red light at night for one week not only reactivated key antioxidant
enzymes at the gene and enzyme activity level at dawn but also contributed to a more
efficient and successful defence against Botrytis cinerea infection.
